What is Magnetism?

Write4U said:
OK, I accept your word for it.
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I encourage you to not just take my word for it, but to investigate it for yourself.

Write4U said:
Hmmmm, I tried it and it came up immediately.
https://en.wikipedia.org/wiki/Magnet#Two_models_for_magnets:_magnetic_poles_and_atomic_currents
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Yes, the page loads, but the section "Two_models_for_magnets:_magnetic_poles_and_atomic_currents" isn't there (anymore). You are effectively pointing to page 300 of a book with only 200 pages.

Write4U said:
As I undersatnd it, taking the earth as an example, the earth's magnetic field surrounds (curves) from pole to pole. To me this presents as a toroidal magnetic field.
240px-SurfacesWithAndWithoutBoundary.svg.png

and

https://en.wikiversity.org/wiki/Physics_equations/Magnetic_field_calculations
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True, but what's "internal" about then? And why did you refer to a field as an "effect"?

Write4U said:
Yes, after further reading, I see that magnetism always has an electric component to it.
Thanks for bringing that to my attention.
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No problem; glad I could help.
 
What confused me is this;
Electromagnet
From Wikipedia, the free encyclopedia
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A simple electromagnet consisting of a coil of insulated wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created.[1] The strength of magnetic field generated is proportional to the amount of current through the winding.[1]

Magnetic field produced by a solenoid (coil of wire). This drawing shows a cross section through the center of the coil. The crosses are wires in which current is moving into the page; the dots are wires in which current is moving up out of the page.
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An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of insulated wire wound into a coil. A current through the wire creates a magnetic field which is concentrated in the hole in the center of the coil. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet.
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The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field.
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According to this article there is a distinct difference between a ferro-magnet and an electro-magnet, both which may satisfy Maxwell's Equation, but one is a dynamic process (energy), whereas the other is a static field existing between two oppositely charged poles.
Electromagnets are widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment. Electromagnets are also employed in industry for picking up and moving heavy iron objects such as scrap iron and steel.[2]
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https://en.wikipedia.org/wiki/Electromagnet
 
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exchemist said: ↑
What is a ferrocell? I've had a quick look on the web but can't seem to find a good description.
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origin said:
Apparently it is a thin layer of mineral oil and ferrofluid between 2 layers of glass illuminated by LEDs. The ferrofluid which is dark lines up with the magnetic field so as you move move the ferrocell through the field it will show different patterns. Sounds kinda fun....
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Indeed
 
NotEinstein said:
Yes. To the best of my knowledge, Maxwell's equations describe everything about magnetism (classically), which would include ferromagnetism....
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No. ME's can't explain ferromagnetism. For that you need QM.

Anyone interested in following an interesting and evidently unrealized (apart fro your's truly) subtle consequence of the classical/quantum interplay is welcome to view my inputs (as kev n), beginning with:
https://www.youtube.com/_watch?v=1bXjB0zrjp0&lc=UgzoKZ0U39pUKoiw0Dx4AaABAg
Then as a series of replies to poster Ken Behrendt (who went off more and more into a pseudoscientific far-reaching 'dissertation') here:
https://www.youtube.com/_watch?v=1bXjB0zrjp0&lc=UgwLPiEH3n3n9waONkN4AaABAg
(expand the 'View all 6 replies').
Note: direct pasting of URL's screws up in SF, so cut & paste above 'crippled' links into browser - then remove the underscore in each link!
I did post on that matter way back here at SF, in more detail in certain respects. But won't link as the reactions were typically negative knee-jerk 'that's un-mainstream!!!' reactions.
 
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Q-reeus said:
No. ME's can't explain ferromagnetism. For that you need QM.
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The question was if situations involving ferromagnetism could be described by Maxwell's equations, which they can. You are right though that for a detailed explanation how ferromagnetism arises in the first place, quantum effects (especially spin) need to be taken into account.
 
NotEinstein said:
The question was if situations involving ferromagnetism could be described by Maxwell's equations, which they can. You are right though that for a detailed explanation how ferromagnetism arises in the first place, quantum effects (especially spin) need to be taken into account.
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question: does "spin" also produce electric current?
 
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NotEinstein said:
No, not directly anyway.
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So is ferromagnetism a retained memory of electric current? I read somewhere that ferro materials are more sensitive to electricity and somehow can retain faint electric influences on spin, aligning the spin in the same direction, which as I understand it is the remarkable attribute of a ferromagnet and creates the pnenomenon of oppositely charged poles.

b) is a ferromagnetic field static or does it indicate a flow of something from one pole to the other?
 
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Write4U said:
So is ferromagnetism a retained memory of electric current? I read somewhere that ferro materials are more sensitive to electricity and somehow can retain faint electric influences of spin, aligning the spin in the same direction, which as I understand it is the remarkable attribute of a ferromagnet and creates the pnenomenon of oppositely charged poles.

b) is a ferromagnetic field static or does it indicate a flow of something from one pole to the other?
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(You'll have to ask Q-reeus; (s)he seems to be more knowledgeable about these matters.)
 
Write4U said:
So is ferromagnetism a retained memory of electric current? I read somewhere that ferro materials are more sensitive to electricity and somehow can retain faint electric influences on spin, aligning the spin in the same direction, which as I understand it is the remarkable attribute of a ferromagnet and creates the pnenomenon of oppositely charged poles.

b) is a ferromagnetic field static or does it indicate a flow of something from one pole to the other?
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It is aligned spins (and orbital motion) of unpaired electrons, which you get in some materials. A circulating electric charge generates a magnetic dipole, so if you get a lot of these lined up they add to each other and give rise to a magnet. As to why they do that in certain materials, that I think is a QM effect to do with the operation of the Pauli Exclusion Principle when the orbitals of adjacent atoms overlap.

But it is not a "memory" of an electric current: in effect, a spinning or orbital electron is itself an electric current, on a tiny scale, because it is a moving electric charge.
 
exchemist said:
It is aligned spins (and orbital motion) of unpaired electrons, which you get in some materials. A circulating electric charge generates a magnetic dipole, so if you get a lot of these lined up they add to each other and give rise to a magnet. As to why they do that in certain materials, that I think is a QM effect to do with the operation of the Pauli Exclusion Principle when the orbitals of adjacent atoms overlap.

But it is not a "memory" of an electric current: in effect, a spinning or orbital electron is itself an electric current, on a tiny scale, because it is a moving electric charge.
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What then keeps a ferromagnet magnetic? Is not the retention of same spin which creates magnetism? In the absence of an electric current, why does the spin of half the atoms not reverse and create a balance which cancels the magnetic abilities of ferromagnets as it does in EM magnets. Not all ferrometals are naturally magnetic, because they naturally have a balanced spin, half left, half right (no magnetism)
Magnetism,
There are three metals with magnetic properties: iron, nickel and cobalt. They are known as ferromagnetic metals. Heating these metals will reduce their magnetization to the point where magnetism is completely eradicated.
The temperature at which this occurs is known as the Curie temperature. For nickel, this temperature is 626 degrees Fahrenheit; for cobalt it is 2,012 degrees Fahrenheit; and for Iron it is 1,418 degrees Fahrenheit.
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Moreover, how can "tiny" (weak) electric charges keep the spin aligned through the entire magnet to produce such a relatively incredible attractive force?
 
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Write4U said:
What then keeps a ferromagnet magnetic? Is not the retention of same spin which creates magnetism? In the absence of an electric current, why does the spin of half the atoms not reverse and create a balance which cancels the magnetic abilities of ferromagnets as it does in EM magnets. Not all ferrometals are naturally magnetic, because they naturally have a balanced spin, half left, half right (no magnetism)
Moreover, how can "tiny" (weak) electric charges keep the spin aligned through the entire magnet to produce such a relatively incredible attractive force?
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Why not just study a scholarly article that explains it? e.g. https://en.wikipedia.org/wiki/Ferromagnetism#Explanation
 
Q-reeus said:
Well, if you continue reading that Wiki article, the very next section in fact.....:cool:
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OK.
The domains will remain aligned when the external field is removed, creating a magnetic field of their own extending into the space around the material, thus creating a "permanent" magnet.
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Thus it seems to be akin to a form of "memory", though it may be caused by physical constraints.?
 
Q-reeus said:
Hmm... skimming through a selection, there are various less than really useful YT vids on ferromagnetism, but this one may help:
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Wonderful. Thank you for that excellent link.
I love the narrative and illustrations. Clear and simple, and has secondary leads to boot.

Whole independent domains (magnetic fields) whithin a ferro object can expand or contract and be manipulated for practical purposes. Neat.
 
Ehm, but what I think you are missing is that if we are looking at it, so measureing it, there is still both spins visible, not only one as if we would measure the electron
 
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